void measure(const Conf& conf, std::size_t stamp) { m_acc(m_op(conf, stamp)); }
void measure(const C& conf, std::size_t stamp) { double m = 0.; for (bool spin : conf) m += spin ? +1. : -1.; m_acc(m); }
inline void operator()( sequence_result_type & sres ) { m_acc( sres ); }